create-react-app is detected automatically and you don't need to customize configuration before build anymore. Set extends to null to disable automatic detection.
Of course, if your app is intended only for electron, electron-react-boilerplate is highly recommended and no need to use create-react-app.
Wonder why 19.x releases are still pre-releases? Because yet another breaking change is expected (AppX target) :)
Are you boilerplate project author — don't worry, extends will soon support shareability as eslint supports and you can move custom configuration out of user's project.